Simple:
Select your page size (under Page Settings) to a 13x19" sheet on your favourite printer (tell it the right printer so it can know about the margin sizes).
Set the Rows and Columns fields to 2 each (thus a 2x2 grid). It will make the cells as large as they can be within those constraints, so you probably want to set the units to Inches and explicitly set the cell size to 5x7". You probably want to turn on "Auto-rotate to fit".
Be aware that to get exactly the size you want you'll need to make sure that your photos are 5:7 aspect ratio before going to print: it'll fit the images into the 5x7" boxes and if you've got a different aspect ratio you'll end up with images that are smaller. Unless you want to experiment with Zoom to Fit.
Make sure you've selected the appropriate 4 photos in the filmstrip, and you're good to go.
Well, you need to set the profile/etc appropriately, but you're mostly there at least.
Isn't this stuff covered in multiple video tutorials around the 'net?